But the man writes that it was developed by "totally unscientific" methods, based upon his observations. Primers, in my opinion, are best matched the powder when it comes to determining performance. There is no "best" primer. The results can be surprising.
In 1988 I made up a test "barrel" in 30-06 that was machined with just a chamber and nothing else. The barrel stub ended ahead of the chamber. This was fitted to a Model 98 Mauser action. Resting squarely against the machined face of the barrel was a machined 4" long rod of equal diameter (2") to the barrel face, which was mounted on a hinged rod, and that to a frame work with a pivot pin. Kind of a ballistic pendulum affair. Attached to the outboard end was a marker from a commercial tracking thermometer that would mark movement of the pendulum on a radially marked graph paper. The idea was that I would fire primers in the "gun" which would cause the pendulum to swing to differing degrees which would be indicated and recorded on the graph paper.
The test case was a single Lake City case which had the pocket reamed for uniformity and depth and the burrs removed. It was then fit to the chamber by fire forming using a dry cereal filler. (During the tests this fire forming needed to be repeated several times due to shortening of the case/headspace)
It took me a couple of weeks of spare time to machine and build this unit and this is what I found: Magnum primers all were about the same, Standard large rifle primers were about the same with regard to average pendulum movement. The difference came when you looked at the spread. Match primers were the most uniform, generally, and non-match were not. About what you'd expect. Oddly, some of the primers I rated as mediocre were the ones I used for my most accurate 500M silhouette loads.
After much thought I decided that there is much more to it than "heat" of the primer. Especially since the "heat" is retarded/utilized by the coatings on the powder to achieve different burn rates and in doing so, influence the pressures. While some powders seem to require a certain primer (I wouldn't touch off 5010 machinegun powder with a small pistol primer) there seems to be a need to mate the primer to the powder and cartridge. My most recent example is my Hornet load. With small rifle primers the loads are good. With small pistol primers the groups were cut in half and the velocities higher. I have my own ideas as to why but I'll sit on them for now.
For now, since we can't control the uniformity of the primers we buy, we as shooter might concentrate on the uniformity of the primer pockets we use them in. It's one of the few accuracy enhancements (to a cartridge case) that I think is worth while in a sporting rifle.~Muir